Method of preliminary treatment for accumulator-plates.



STATES PATENT OFFICE.

" HENRY EITNEa'oF' MAYBURY, WOKING, ENGLAND.

METHQD or PRELIMINARY TREATMENT FOR AOCUMULATOR-PLA'IES.

Specification of Letters Patent.

Patented Oct. 1, 1907.

Application filed August 25, 1904. $erial No. 222,162.

'others skilled in the artto which it appertains to make and use the same.

My invention refers to an improved process or method for bestowing a preliminary treatment on'accumulator plates by the use of which the formation of the plates so treated as electrodes on the Plants principle, is greatly facilitated. and improved.

A leading feature of my invention consists of the practical utilization. of the discovery which I have made that 'the rapid forming effect obtainable by the use of very dilute or attenuated solutions can be greatly increased by the use of high current densities, provided that the temperature resulting from the use of high current. density is prevented from rising so high as t exercise a prejudicial effect upon the plates while subjected to the process.

In carrying out my invention in practice I employ plates of cast, stamped, perforated old laminated lead of any shape or form suitable for a Plante electrode,' and subjectthe same as anodes to the action ofan electricscurrent in an electrolyte, consisting of a highly attenuated or dilute solution of a suitable sulfate or' sulfates, to which mere traces of substances capable of forming soluble lead compounds, preferably chlorids,

. these inetals may be employed, but the effect of action' I depends upon the proportions not being practically exceeded.- But I have also found that very dilute acids maybe employed with equal and even better effect. An acid electrolyte which gives admirable results consists of water acidulated with from s to 3% per cent. of pure sulfuric acid of sp. gr. of 1.820 to which s to 3% parts per 1000 of pure hydrochloric acid containing 28 per cent. HGL have been added. I

' It is preferable in carrying outthis process that th distance between anodes and cathodes should be considerable, and that the current density employed should be as great as possible, namely preferably such asto raise the temperature of the electrolyte to from 75v to 85 F. but not to exceed the latter temperature.

l'n order to facilitate and increase therapidity of the process, I may artificially cool the bath of electrolyte in which it is being carried out by any convenient tion thereby economizing current.

' means, such as a stream of running cold water arranged to traverse a tank in which the cells or vessels in which the process is being carried out are arranged or by sur rounding them with a freezing mixture, or dissolving salts around them, the solution of which is accompanied by a fall of temperature. By this means I am enabled to shorten the process by using higher current densities without causing the above mentioned limits of temperature, which would be prejudicial to the plates if exceeded, to be surpassed. The best results are obtained by so adjusting the temperature and current density that within a period ranging from 18 to 46 f hours the whole surface of the plates treated as anodes becomes converted into a granular highly oxidized layer or pellicle penetrating everywhere to the same depth (which can be predetermined)and not displaying the slightest trace of corrosionor irregular action. The plates which have, been thus treated as anodes are then subjected to certain liirtherjmanipulations and processes. Firstly, they areimmersed'in running water or water that is frequently changed in which they remain for some length of time in order to cleanse and consolidate the oxidized layer, Thereafter the plates are treated as cathodes in any convenient innocuous electrolyte, such as very, dilute sulfuric acid. In this way all the highly oxidized lead particles are converted into granular yet finely divided particles of electrolytic lead firmly adherent to the surface of the elec trode and its laminations. As a variation of my process I may performthis reduction in the same solution-in which the plates were in the first instance formed. The electrolytic action taking place-in this process to some considerable extent reconstitutcs the electrolyte composition, enabling a second set of positive electrodes to be partly formed simultaneously with the said reduc- As a further variation I may'instead of the used electrolyte employ an electrolyte consisting of water to which more traces of substances sufiicient to render it conductive to the electric current are added. The plates which are being reduced in that case contribute to the electrolyt by reducing the substances necessary for the fbrmation of the positive plates.

After reduction the reduced electrodes are allowed to remain in water for a moderate length of time andv are subsequently exposed to the action of dry, warm air, which has the effect of gradually oxidizing the finely divided electrolytic lead layer into a lower oxid.

of lead and the whole mass becomes gradually very firm and tenacious.

The plates or electrodes after having undergone the processes above described may be built up intosections and formed either into negatives or positives ,but are more specially adaptedfcr use as the latter. They may be formed at once in sulfuric acid of the ordinary strength employed in accumulators and will not he injured it formed in acid of even somewhat greater strength, while three or [our discharges are sutlirient to give the plates a full and high capacity.

The formula of sulfuric acid being H 80 I have herein considered it as a sulfate, the formula being analogous to that, of sodium and potassium sulfates.

-I- claim 1. The process oi preparingelectrodes for secondary hat: teries. which eons ts in immersing the plate in a weak electrolyte. comp ln g' a sulfate solution containin not more than three and oiie-halt per cent. of the sult'al' to which is added not more than three and one-half parts per tool) at a t-hlorid, and snhjectine' the plate as an anode to an electric current of as hie-h density as possible. without the temperature of the electrolyte ahove H3 l cially cooling the electrolyte to permit the use of a higher current density than could otherwise he employer]. then washing the plate to cleanse it and consolidate the oxidized layer. then treating the plate as a cathode inan innocuous electrol \'te. treating; the plate with water and then exposingit to the action of warm air. suhstant rally as descrihetl.

'lhe process of preparing electrodes for secondary hatiillitlll is added not: more than three and one-half parts per 101m 01 a chlorid. and snlijeeting the plate as an anode to an electric current oi as high densitv as possihle withou ra' 'in: the temperature of the electrolyte ahrire :lii" I i, artit tally eooling the electrolytev to permit the use oi a hi ahei current. density than cou otherwise he etnployml. sulisIantiaIIy as described.

3, The process of preparing electrodes for seconda y hat teries which consists in immersing the plate in a weak electrolyie comprising a sulfate solution containing not more than three and one-half per cent. of the sult'at to which is added not: more than three and one-halt parts per taoa of a chlorid. and snhjectim: the plate as an anode to an electric current oi as high density as possible, without raising the temperzu re oi? the electrolyte ahor cs3 Ft, suhstantially as described.

A. In a process of preparing electrodes for secondary hatteries. immersing; the plate in a weak electrolyte W at prising; not more than three and one-halt per c out: ot' t'uric acid. to which is added not. more than thrt' and one haltparts per ltltitl of hydrochloric acid, subjecting; the plate as an anode to an electric current of high density and maintaining the electrolyte at: a temperature of not. more than 83' ll. suhstantially as descrihetl.

in witness wherenl' l have hereunto set my hand in the presence of two witnesses sul- lll NltY Ll'll'lNl lit. Witnesses lHCllAltl) Norman Lucas, 1:, SMITH. 

